Batch classes are a key tool in Salesforce for processing large amounts of data in a more efficient and scalable way. They are particularly useful when you need to perform a specific task on a large number of records, such as updating a field, deleting records, or sending emails. In this article, we will walk through the steps for using batch classes in Salesforce, including how to create a batch class, how to execute it, and how to monitor its progress.

Step 1: Create a Batch Class

To create a batch class in Salesforce, you will need to define the scope of the batch process using a SOQL query. This query specifies the criteria for selecting the records that will be included in the batch. For example, you might want to select all accounts with a particular type of industry, or all contacts with a specific email domain.

Once you have defined the scope of the batch, you will need to define the actual batch processing logic. This is done using the Database.Batchable interface, which requires you to implement three methods: start, execute, and finish.

The start method is called when the batch class is first executed, and is typically used to set up any necessary variables or initialize any objects. The execute method is called once for each batch of records, and is where you will define the actual processing logic. Finally, the finish method is called when all of the records have been processed, and is typically used to send an email or perform some other final task.

Here is an example of a simple batch class that updates the Industry field on all accounts:

global class UpdateAccountIndustryBatch implements Database.Batchable<sObject> {
  
  // Query to select all accounts
  global Database.QueryLocator start(Database.BatchableContext bc) {
    return Database.getQueryLocator('SELECT Id, Industry FROM Account');
  }
  
  // Update the Industry field for each batch of accounts
  global void execute(Database.BatchableContext bc, List<Account> accounts) {
    for (Account a : accounts) {
      a.Industry = 'Technology';
    }
    update accounts;
  }
  
  // Send an email notification when the batch is complete
  global void finish(Database.BatchableContext bc) {
    Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage();
    mail.setToAddresses(new String[] {'admin@example.com'});
    mail.setSubject('Update Account Industry Batch Complete');
    mail.setPlainTextBody('The batch process to update the Industry field on all accounts has completed.');
    Messaging.sendEmail(new Messaging.SingleEmailMessage[] { mail });
  }
}

Step 2: Execute the Batch Class

Once you have created your batch class, you can execute it using the Database.executeBatch method. This method takes two arguments: the batch class itself, and the batch size. The batch size specifies the number of records that will be processed in each batch. Salesforce recommends using a batch size of 200 or less.

Here is an example of how to execute the UpdateAccountIndustryBatch class with a batch size of 200:

UpdateAccountIndustryBatch updateBatch = new UpdateAccountIndustryBatch();
Database.executeBatch(updateBatch, 200);

Reference Salesforce Document: Batch Class